Abstract
A new polynuclear cationic complex of copper(II) (Cu(II)) with pyrazine as a ligand and perchlorate acting as a counter-ion was obtained. X-ray diffraction results accounted for a 2D polymer array of cations, in which the metal-ions were located on an ideal square-pyramidal coordination environment defined by four nitrogen atoms of pyrazines and one chloride. The polymer compound, which extended along the ab plane of the structure, showed Cu(II) displaced 0.9 Å from the plane defined by the N-atoms and chloride. Perchlorate ions were situated in cavities interacting with pyrazine by anion-π weak interactions. These low-energy bonds emerged as a consequence of the π-acidity of pyrazine upon coordination to Cu(II). Density-functional theory (DFT) calculations at the M06-2X level of theory using 6-31G(d) and 6-31+G(d) were conducted aimed at achieving an electronic description of selected properties of title complex. M06-2X/6-31G(d), in particular, proved to be an acceptable performer in dealing with geometric aspects keeping the computational cost very low.
Highlights
Nitrogen heterocycles are ligands of paramount importance in coordination chemistry
To shed light into the electronic properties, geometry optimization and population analysis were performed with the density-functional theory (DFT) hybrid meta exchange-correlation functional M06-2X [17] combined with 6-31G(d) [18, 19, 20, 21, 22, 23] and 6-31+G(d) [24]
Population analysis for [CuCl(pyz)4]+ obtained with M06-2X/6-31+G(d) shows the metal center carrying a charge of +1.021, which is markedly smaller than the formal charge of +2 as a result of a donation process, in which chloride ends with a charge of −0.665
Summary
Nitrogen heterocycles are ligands of paramount importance in coordination chemistry. Pyrazine (pyz), which is an N ,. With copper(II) (Cu(II)), in particular, pyrazine plays a remarkable role for building Cu coordination polymers. Polymer complexes of Cu(II) with pyrazine-containing ligands exhibit, in some cases, potential applications as gas storage system, chemical catalysis, and drug delivery, among others [14, 15, 16]. As a part of our interest to increase basic knowledge on structural properties of Cu(II) complexes containing diimine ligands, the synthesis and structure of a polymer array of. Cu(II), pyrazine, and chloride containing perchlorate as a counter-ion are presented. The network extends along the ab plane of the structure, in which the metal-ion is observed slighty displaced from the plane defined by the N-donor atoms. To shed light into the electronic properties, geometry optimization and population analysis were performed with the density-functional theory (DFT) hybrid meta exchange-correlation functional M06-2X [17] combined with 6-31G(d) [18, 19, 20, 21, 22, 23] and 6-31+G(d) [24]
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